The BALB/3T3/A31-1-1 mouse embryo cell line, previously characterized for assays of toxicity, neoplastic transformation, mutation and DNA damage/repair, was used to investigate the cellular reaction to inorganic particulates having in vivo carcinogenic activity. The particulate samples were in the respirable size (1-5 microns) and included the following types of crystalline silica: quartz (Min-U-Sil, HF-etched Min-U-Sil, DQI2, F600 and Chinese quartz), cristobalite and tridymite. Control dusts included amorphous silica and ferric oxide. High phagocytic activity was demonstrated by these cells. Dust-laden cells were amenable to subculture even after 6 weeks. Dose-dependent toxicity was induced by crystalline silica dusts. Neoplastic transformation was induced by quartz in a dose-dependent manner, but could be impeded by excessive toxicity resulting in delayed cell lysis and regrowth. Ferric oxide dust remained in phagocytic storage in cell monolayers for 6 weeks without inducing transformation. Foci of silica-transformed cells were subcultured and cryopreserved for molecular characterization.